Enteric coating has been widely used for various purposes of mainly protecting medicaments unstable to acid from the gastric acid, protecting gastric mucous membrane from medicaments stimulating or damaging the stomach wall, and the like. Many tablets containing an active ingredient and an alkali component, which are coated with an enteric coating agent are known (patent documents 1-17). In addition, use of a methacrylic acid copolymer as an enteric coating agent is known. The methacrylic acid copolymer is commercially available as EUDRAGIT (registered trade mark); manufactured by Evonik Industries AG) polymer. In addition, Acryl-EZE (manufactured by Colorcon Ltd.) added with sodium bicarbonate (alkali component) as an enteric coating substrate in advance for improving polymer dispersibility is also commercially available. Moreover, it is known that talc is generally used as a lubricant in an enteric coating agent, and the content of talc is preferably 50% (weight ratio) relative to the polymer component (non-patent document 1).
As a compound showing a serotonin reuptake inhibitory action, and useful for treating affective disorders, such as depression, and anxiety disorders including generalized anxiety disorder, panic disorder and obsessive disorder, 4-[2-(phenylsulfanyl)phenyl]piperidine derivatives (patent documents 18, 19) are known.